Electromagnetic brake mechanism



:s sheets-sen 1 rl.. s. Bunce-rr ELECTROMAGN'ETIG BRAKE MECHANISMS med-June za. 194:5

March 2., 1948.

-Maljch 2; 11948. .\s. BURGETT y ELEGTROMAGNETIC BRAKE MECHANISMS Filed June 28, 1943 3 Sheets-Sheet 2 afas- I az IN VEN TOR BY yn/7 5L/rye# Y w QAZJ'/ vae/rif Patented Mar. 2, 1948 ELECTROMAGNETIC BRAKE MECHANISM Lyn'n s. Buma. Eueua. ohm.` assignmto. The Clark Controller Company, Cleveland, Ohio, a

corporation of Ohio Application June 28, 1943, Serial No. 492,512

Momma. (criss-171') 1 This invention relates to brakes; and in some aspects relates to electromagnetically actuated brakes. y

The invention is in, that general class of brakes in which brake shoes are normally spring-biased into engagement with a brake drum. and are released therefrom by energization of an electromagnet; but as will become apparent hereinafter Some of the features and principles of'my invention are applicable to brakes other than electromagnetic brakes.

There are numerous objections to prior brakes of this class and the present invention consists in improvements for overcoming these objections; and consists further in other improvements generally in brakes of this class; and some \of these improvements are set forth below in the objects of the invention.

It is among the objects of the invention:

To provide generally an improved brake of the y class referred to;

To provide a brake of the class referred to having improved means for adjusting it .at the time oi' manufacture and/or inthe field;

To provide in a brake of the classl referred to improved adjustment means for taking up wear yof the shoes and drum;

To provide in a brake of the class referred to improved means for equalizing the normal clearance between the shoes and drum;

To provide, in a brake of the class referred to, an improved construction by which the twisting or bending strains in the main frames of prior brakes are avoided;

To provide in a brake of the class referred to 4 means by which adjustment at a single point ad- -Justs the brake shoes to take up wear; and by which concurrent readjustment of the brake operating spring, or theoperating. stroke of the brake magnet, or the respective clearances of the brake shoes and drum, etc., is made unnecessary.

To provide improved means for maintaining the brake shoes respectively spaced from the brake drum when in non-braking or released positions, which means is self adjusting to render its operation uniformly enective for different degrees of wear of the shoes;

To provide an improved construction and mode of operation of a brake magnet winding retaining element;

To provide a brake of the class referred to the parts of which are readily accessible for adiustment; and which permit the drum to be removed from the brake conveniently and quickly;

To provide yin a, spring operable electromagferred formvwith .l-l ofFig. 1

ytaining plate in-a magnet shell which netically releasable brake, means for manually locking the brake in released condition, which means is automatically rendered ineffective t'o lock the brake, upon energization of the electromagnet winding;

To provide a brake of the class referred to comprising improved means by which a single adjustment compensates for Wear of the brake shoes and also concurrently restores other parts to their optimum originall functioning relations if wear on. the shoes has changed these relations.

Other objects will be apparent to those skilled in the art to which my invention appertains.

The invention is fully disclosed in the followingdescription taken in connection with the accompanying drawing in which:

Fig. 1 is a front elevational view of a. brake mechanism embodying my vinvention in its preparts `broken away and parts in cross-sections; r'

Fig. 2 is a top plan view of the embodiment of Fis.1:

Fig. 3 is a sectional view taken from the plane a-s of Fig. 1 with parts behind the section plane omitted; y

Fig, 4 is an end elevational view taken in the direction of the arrow 4 of Fig. 1;

Fig. 5 is a sectional view taken from the piane with a brake drum of that figure omitted; i

Fig. 6 is a view similar to a part of 1 but with certain" operative parts thereof in diii'erent positions; g Figs. '7, 8, 9, and 10 are somewhat diagrammatic views illustrating the mode of operation of` -a brake shoe positioning means which is illustrated in Fig. 1;

Fig. 11 is a fragmentary sectional view taken approximately from the plane Il of Fig. 1 and with one of the parts behind the section piane illustrated in cross-section for clearness;

Figs. V12 and 13 are views illustrating the means and method of securing a. magnet winding replate and shell are also shown inFig. 1;

Fig. 14 is a view illustrating a means which I f may employ for retaining removably pivot pins which are shown in Fig. 1 without said means; Fig. 15 is a sectional view taken from the plane ls-ls of Fig. 14 with the parte behind the lsec- 1 tion plane omitted;

Fig. 16 is a view similar to Fig. 15 with the parts in different relative positions to s how the mode of operation thereof; f f

y Fig. 17 visa view .to reduced scale of a part of Fig. 1 illustrating a modiflcation which I may employ; i

Fig. 18 is a view of the parts of Fig. 1,7 in different positions which they may assume in the operations thereof.

Referring to the drawing it will be seen that the brake mechanism is of the unitary type by.

which it may be transported and mounted in position as a unit and to this end the parts of the mechanism are assembled upon a main frame or base. l'Ihis frame or base may be variously constructed, but I prefer to provide therefor a pair of longitudinal steel base members I I transversely spaced apart and rigidly connected together by a pair of longitudinally spaced apart transverse base members 2 2.

' As indicated hereinbefore, the brake is of the j `8 to a lower portion of which feet 9 9 are welded,

and these feet are bolted to brackets Ill-I0 on the longitudinal base members I I wherebyV the shell is rigidly connected to the base members. To facilitate manufacture, the brackets I0 I0 may be made of steel and welded to the base members, and the feet 9 9 may be secured to the brackets by bolts projected therethrough as shown.

The shell 8 is preferably made in the form of a band or hollow cylinder of steel and at one end, the right hand end as viewed in Fig. l is closed by an end plate II preferably lwelded thereto. A magnet core I2 is welded at one end, the right end as lviewed in the drawing, to the plate II and the magnet winding 5 is disposed around the core I2 and within the shell 8.

By means of this construction as will be apparent, the magnet winding is completely lenclosed in a steel housing except for its forward or left face as viewed in the drawing and thereby provides a well known type of electro-magnet.

.The left face of the Winding is also covered and protected and retained in the shell by means to be described later.

Projecting upwardly and forwardly from the magnet shell 8 is a pair of armature supporting arms I3 I 3, transversely spaced apart and having axially aligned bores through which an armature shaft I 4 is projected, and the armature supporting arms I3 I3 are preferably provided by making them from steel and welding them to upper portions of the magnet shell 8. As plainly shown in Fig. 1, the shaft I4 is supported as described in a position forwardly of the magnet, the purpose of which will presently appear.

A magnet armature I5 is provided. in the form.

of a steel disc confronting the forward or left hand edge of the shell 8 and the left hand-end of the core I2 and is mounted to swing toward and from the magnet by means of armature arms I6 I6 preferably formed from steel and welded to upper portions of the armature and bending forwardly and upwardly and in their end portions being provided withbearing bores embracing the 4 shaft I4 whereby the armature is mounted to swing on the shaft.

The magnet core I2 has a bore I'I extending co-axially therethrough and the aforesaid spring 6. preferably a helical compression spring, is disposed in this bore with one end lodged in a recess I8 in the armature I5 and with the opposite end engaging a head I9. A spring tension adjusting screw 20 is threaded into a bracket nut 2I which is bolted to the end plate II,-and the screw 20 is disposed substantially co-axial of the spring 6 and its inner end pivots .upon the head I9 whereby, as will be understood, upon turning the screwthe tension of the spring may be adjustably varied, and by means of a lock nut 22, locking the screw 20, the adjustment may be fixed.

The means by which the magnet winding 5 is retained within its steel housing described and covered and protected therein will now be described, reference being made to 1, Fig. 12, and Fig. 13. kA brass or other non-magnetic metal disc 23 is made of such diameter that it substantially fits within the shell 8, and in its central portion is provided with a large perforation 24 through which the spring 6 passes; and the central portion of the disc 23 is secured upon the end of the core I2 by a plurality of screws 25 projected throught the disc and threaded into the end of the core. At its periphery, the disc is provided with a` plurality such as four notches -26 preferably spaced or scattered around the periphery and the notches 26 are, circumferentially, wide enough to admit the end of an .ordinary screw driver. At each side of the notches, the peripheral edge of the disc is bevelled as shown at 21 for a substantial distance such as an inch or more at each side of the notch.

When the disc 23 has been mounted as referred to, the central portion of the disc is secured by the screws 25 as referred to, and the periphery of the disc is also secured within the shell by a peening operation as follows.

A center punch 2s or other suitable tool is presented to the metal of the shell overhanging the bevel on the disc as shown in Fig. 13 and the 4metal of the shell is peened down over the bevel.

and using the screw driver as a lever, the disc is pried out of the shell, forcibly passing over the peened portions of the shell. When the disc 23 is thereafter replaced, its periphery is again secured in the shell by the repetition of the aforesaid peening operation, the metal of the shell being peened over the bevel of the disc at fresh points of the shell.

It has been found in practice that the disc 23 will have to be removed as described only a few times within the entire life of the brake so that a relatively shortlbeveled portion on the disc to provide for a succession of peening operations will be sufficient, and for this reason bevels 2l of relatively short circumferential extent have been shown; but it will of course be understocd thatif preferredfor anyreason. the bevel. canv be-extended all the` wayaround .the periphery off the non-magnetic disc Il.

Returning again :tot the brake shoe operating'` mechanism,. it will be seen; from the foregoing that wheny the magnet windingi is energized, the magnet armature `I5 will ber-moved or'swung'coun.-

terclockwise; and that when the winding is deenergized the spring- 6. will move the armature l5 clockwise andthe mechanismv causes this movement-to respectively-release the brake shoes from 1 the druml or set them in' braking engagement therewith. The contacter orother control means for controlling currentcto the winding has not been shown inasmuch as this is so well under-- stood in'this art.

Projecting downwardly and forwardly fromthe. llower portion of thev armature l5 is a'pair of Upony thaupper end of the frame 4i is provided ys pivot. bearing and it :preferably consists of a pair-ofslugs-ll-l-l secured by preferably welding them tothe tie member v andv supporttransversely spaced arms 2li-29'. Pivotally sup-v 4 ported on these arms. 29--29` isa substantially vertically extending frame shown generallyvat 30. l

This frame 30 may be variously constructed, but

preferably it consists of a pair of transversely mounted upon this frame- 30. These. brake shoes.y may be of known construction in general and the exact form and construction thereofV constitutes no partv of the present invention, and theyth'erel fore may comprise. a brake shoe body 3.5' having an arcuate portion a'and a brake shoe lining 31 concentric with the'vdr'um and engageable there.-

with. On a 'lower portion of the brakeA shoe body is a device cooperating with a device on the main frame, which does constitute part of the present invention and will vbe described later. '.Io mount. the brake-shoe on the said frame 30, the body,y portion may conveniently bedisposed betweenithe.`

by a pin 38. projected through the uprights and.

upon which the shoe bodyhas oscillatory bear-K ing.

At the upper end of the said frame -ilis a 'pin bearing and itis preferably providedbywelding a pair of upwardly extending lugs 39-39 .to

the upper tie' member 33 and. providing co-axial bores in the lugs and disposing apivot bearin pin 40 therein. y

At this pointis may be noted that the four bearing pins above described andnamely, Il; 18,

l0, and Il are all disposed vin generally a common vertical plane and that this is intentional and.

introduces functions anda mode of operation and advantages which will 'be discussed later.

The othery brake shoe 3 on the left endofthe mechanism as viewed in the drawing is also mounted on a frame shown generally at M and.

this frame also preferably. consists ofy a pair of uprights 42`42 spaced apart and connected by tie members 43 and M preferably formed..

ing.: a transverse pivot pin Il.-

' The pivot'pins 40 and 48. above. described- Vare connected'with each other by a linkage or tie rod of adjustable length shown generally at I0. Adjustment of the length of this tie rod. may beprovided` byvarious means. but I prefer to make it of generally the turn-buckle type and to this end preferably I. provide a tie rod yhead 5I having bearing on the pin Il Abetween the lugs I8, a tie rod head l2 having bearing on the pin Iiibetweenthe lugs SI-II, a tum-buckle bolt 53 having right'hand threads on one end and left hand threads .on the other threaded respectively into the heads ll and I2, and having an intermediate portion 54 of hexagonal. or other polygonal cross-section suitable to be gripped by a wrench 4for 'turning the bolt, and lock nuts 55-55 ony the threads, which may be turned to lockingly engage the said heads and bolt threads to. lock the bolt in adjusted rotational positions. 0n the threaded e'nd of the bolt 5I, which is screwed int the head 52 are a pair of lock nuts STI-51, which may be unlocked from each other r and by turningl'them moved along to different positions on the threaded end il 'and then locked in such position and when so locked provide an abutment on the bolt and this abutment cooper- 'ates with a removable stop shown generally at This stop` .is preferably stationary relative to the main frame of the structure T for a .purpose to .be referred to, it lades able that it bev removable, and to this end the ypreferred construction is to provide as shown a U-form member `ll, the legs of which are pivotally supported upon the pin ll and the closed end of "il the U carryingthe stop 5l, th latter being in the form of a downwardly open'- perforation embracing the turn-buckle rod on the left hand end ofthe iockvnuts 51-51 ami engageabie therewith. To4 remove this stop Il for a purpose tol be referred to, the entire U-.form member v58 isv swungI upwardly clockwise around its pivot support pin- Il and may take up, for' example, the

position shown at IIA inbraken line.

. In the lower left hand corner of Fig. 1, is'. shown a spring lllhaving a. main body po on of'helicalform telescoped .upon the shaft 41. and having free end portions Il and 62, the end l! lying upon 'any suitable abutment on the mainframe,

`for example lying uponthe adjacent transverse space member 2; andthe other end l2 being formed into aneye and secured to the tie member I3' referred to above, by means of a bolt 83 projected through theeye and threadedinto the from steel and welded together into a unit, and

the brake shoe is preferably like the one'on the othery side of thevdrum and its body 35 is oscillatably ymounted between the uprights4242 upon a pin 46 supported'upon the uprights; but

it'will be observed that .this frame Il is pivotally connected to andsupportedzupon the mainframe by means of a pin or shaft ll'mounted onthe' longitudinal base members i-l.

tie-member. This spring is formed so that it is under tension when installed as Just described to exert. a counterclockwise resilient torque on the frame 4| tending to rotate itin the counterclockwise direction about its lower pivot support or shaft". l

The operation of the mechanism as thus far .describedrwill now be given, consideringthe parts as moving from the brakedisengaged position to the engaged position illustrated in Fig.r 1.

When the magnet winding 5 is de-energized to allow the brake to set, the spring I, reacting upon the magnet armature I5, swings it clockwise around its supporting pivot Il and thereby moves y the pivot Il atv the lower end of the frame Il .toward the left as viewed in the drawing. Mo-

7 mentarlly, the pivot 40 at the upper end of the -frame 30 is held toward the left as viewed in the drawing by the spring 60 in the lower left hand corner, which as described, holds the frame 4| -toward the left.

The frame 30 therefore pivots around the pivot 40 in the clockwise direction, which moves the brake shoe pivot 38 `toward the left engaging the right hand brake shoe with the drum. Continued r`swinging movement of the armature l5 now causes the frame 30 to be pivoted around the brake shoe pivot 38, which moves the pivot 40 toward the right as viewed in the drawing and this movement acting through the tie rod 50 rocks the frame 4| clockwise on its pivot 41 against the tension of the spring 60 and moves the left hand brake shoe into engagement with the drum; and then both brake shoes are frictionally engaged with the drum by the tension of the spring E, the degree of the braking friction being determined by the adjustment of the tension of the spring 6 as described.

Upon energizing the winding 5 to release the brake, the reverse of these movements takes place, the spring 60 contributing to the movement of the parts to release both shoes from the drum- The adjustment provided `in the mechanism above described will now be considered.

It may be stated at the outset'that the pressure engagement of the two brake shoes with the drum is automatically equalized bythe inherent arrangement of the parts. This may be variously described, but one way to state it is that one brake shoe after engagement with the drum functions as a fulcrum for a lever system for engaging the other brake shoe and the leverage system has a one-to-one ratio.

When the brake mechanism is rst installed for operation, the brake shoe linings being new are relatively thick and the brakel shoes must be positioned, so that the linings will not drag upon the drum when the brake shoes are released; and after a period of use the brakeshoe linings, and to some extent the drum, wear and hence it is desirable to be able to adjustably move the brake shoes toward and from the drum to provide an optimum amount of clearance therebetween at the start of use and from time to time as wear develops. Y

Also, it is important to be able to adjustably position the brake shoes so that the clearance between one brake shoe and the drum is the same as between the other and the drum.

In the mechanism here described, the amount l of clearance of the brake shoes with the drum is determined by the length of the tie rod 50 which' in turn may be varied by turning the turn-buckle bolt in one direction or the other; and the equalization of the clearance is determined by moving the lock nuts 51 along the turn-buckle thread 5S in one direction or the other.

To illustrate, if we assume that the magnet is energized to release the brake shoes, and the armature I5 is accordingly held against the magnet, this will determine a position for the pivot 34, The spring will retract the left hand brake shoe until the lock nuts 51-51 have moved into engagement with the stop 58, thereby holding the left hand brake shoe away from the drum and rocking the upper end of the frame 30 counterclockwise to pull the right hand brake shoe toward the drum. The positions of the brake shoes relatively to the drum are thus determined when the lock nuts 51-51 have moved into engagement with the stop 58. and obviously, ifthe clearances of the brake shoes with the drum are not equal they may be equalized by moving the l-ock nuts one way or the other along the thread 56 of the tie rod. As will be apparent from the foregoing, when the brake is set by the spring 6, the lock-nuts 51-51 will move away from the stop 58, leaving a space therebetween, and the width of this spacewill become greater and greater as the brake shoe linings 31-31 wear -brake shoe linings and be guided by his observation to seasonably renew the brake shoe linings.

It is believed obvious that the clearance or distance between the shoes and the brake drum, after they have been equalized will be determined by the total length of the tie rod between its pivots 40 and 49 and this can be adjustably changed by turning thetie rod in one direction or the other as described; the pitch of the right hand and left hand threads of the tie rod would, of course', be alike so that upon turning the rod to change the clearance does not change the equality of the clearance already predetermined by the adjustment of the lock nuts 51.

It has been found that when the clearance of the two 'shoes with the drum have oncebeen equalized as just described, it does not change over a very long period of use, if ever in the lifeturn-buckle bolt 5,3; and this adjustment is lo-` cated on the outside of the apparatus, where access to it may be freely and conveniently had.

In prior brakes, various other adjustments have been provided and have been necessary, because the readjusting of the brake shoes for wear has thrown other parts out of adjustment and they have had to be concurrently readlusted, such other readjustment including in some cases adjustment of the spring which sets the brake. adjustment of the air gap between the armature and the magnet, restoring of the equality of clearance between the respective shoes and the drum etc. 1

In the present brake, however, when these quantities and relations have once been established in the brake, they may change yperceptibly from their original vstates as the brake shoes wear, but when the brake. shoes are brought back to their original clearance to compensate for wear, and by the one simple adjustment above described, these other quantities are thereby restored to their original state or condition. For example. as the brake shoes wear in usethe armature I5 tends to move farther and farther away from the magnet and the spring 6 becomes more elongated and exerts a lesser braking `force and because of the greater gap thus effected between the armature and the magnet the action of the magnet may become more sluggish upon releasing the brake, but all of these factors are restoredl to their original optimum condition, when the brake shoes are readjusted for wear and allof this is accomplished bythe one simple adjustment described.

aemeo In the practical use of brakes o! this class. it

have provided an improved mechanism for so locking the present brake and this will `now be described.

Ay pair of lugs 64-64 extend rearwardly and ,'dependingly from the end plate or backplate II of the magnet, and may conveniently be provided by making them of steel'and welding them to the plate; and in their lower end portionsV 'are provided with a pivot bearing pin 65. A lever.

66 is pivoted at one endl on this pin 65; and the lever itself carries a pin 61 upon which is pivoted one end of a latch or'lock element 68, which Aextends forwardly under the magnet-toward the magnet armature and preferably being disposed between the longitudinal base members I and 2, as shown, and on its free end carries a latch hook 69, which, as will presently appear, is adapted to hook over the lower edge of the armature I5 to lock it in the brake releasing position. In the normal use of the brake, the lock element 68 hinges downwardly around its pivot 61 and rests upon an abutment 92 with the hook 69 out of armature engaging position.

The lever 66 is normally held in the position of Fig. 1 by a latch In pivotally supported in any suitable manner upon an upper portion of the magnet plate II and having onit's free end a latch hook 89 hooking under and around a pin 90 on the lever, see Fig. 1. The disposition of the pivots 65and 61 is, as shown, such that when the lever 66 is moved clockwise the lock element 68 and hook 68 are projectedforwardly.

When it is desired to operate this lock, the lever 66 is rocked counterclockwise by hand sufciently to release the pin 90 from the latch 10. This is the position of the lever in Fig. l;

-the position of the lever when latched by the latch I on the pin 90 is a more clockwise position than that shown in Fig. 1, although the lever 66 may stay in the position of Fig.l 1 by gravity.- The lever when unlatched is rocked clockwise which projects the hook 69 forwardly, and the lock element 68 carrying the hook 69 -is then rocked on its pivot 6'I upwardly by hand to raise the hook 69, so that it overlaps the lower 'end of the armature I5. The lever 66 is then rocked counterclockwise again, thereby retracting the hook 69 and causing it to engage the lower edge of the armature I and draw it towards the magnet into the brake releasing position and this brings a pin'II into position where it may be engaged by the 'hook 89 of the latch 10, and the latch 'lIl is correspondingly raised to engage this pin and this holds the lever 66 in that position, holding the brakeshoes released. correspondingly, to unlock the brake shoes, the lever 66 is rocked counterclockwise, sufllciently to permit unhooking the latch 10 fromvthe pin 1I and then the lever 66 is rocked clockwise which projects the lock element 68 forwardly and disengages the hook 69. from the armature and the lock element 68 then hinges downwardly by gravity and the lever V66 may be restored to its original position, where it is held by the latch l0 engaging the pin 90.

After locking the armature in the brake released position by means of the hook 69 and lever 66 as described, 'and with the Ilatch 10 holding the parts in locked position, considlo o erable time may elapse while the brake or'the apparatus, which it controls, is being repaired or overhauled as referred to, and after this has been done and the brake is ready to be used, the mechanic in charge of the same may forget to unlatch the lock. The locking arrangement above described is rendered foolproof in this respect as follows: It is customary in electro-magnetic brake practice to provide an electric controller controlling the energization of the brake releasing electromagnet in connection with the apparatus controlled bythe brake so that before the apparatus to be controlled can be operated the brake winding must be energized for release ofthe brake. Accordingly, after overhaul or repair, as referred to, the rst time that the apparatus is again operatedpthe brake winding would be energized.

Also, as will be observed, in order to get the hook of the latch 10 over the pin 1I, the lever 66 and pin 1I must be moved inwardly a short distance beyond their latching positions and then be allowed to settle back to the latching positions after the latch, 'III has engaged the pin 1I, so that in the locked position of the parts as described, and as will be clear, the armature I5 is not tightly engaged with the steel parts of the magnet housing, but is slightly Vspaced therefrom particularly at the lower edge of the armature as viewed in Fig. l.

Therefore upon the energization of the brake winding the ilrst time after the lock had inadvertently been left in` locked condition. the armature I5 will move to take up the aforementioned small space .and because of the magnetism produced by the winding the lower edge portion of the armature will be magnetized and the hook 69, which to this end of course would be made of steel, will be magnetically attached to the armature and stick toit andI move with it. A small rearward movement of the lock element 68 is thereby eiected which, due to the arrangement of the pivot pins 61 and 65 will rock the'lever counterclockwise suillciently to disengage the pin 'II from the latch hook 89. The latch I0 will accordingly fall by gravity and to insure that this will occur and to prevent the latch 10 from adhering magnetically to the leverl 66 and pin 'II if these parts should be made from steel, the -latch 10 is preferably made of non-magnetic material suchasbrass. t v

The brake is now in the condition to set when I the winding is de-energized and the locking arrangement is ineffective to hold the brake shoes released. and when the magnet is de-energized to set the brake shoe, the` armature I5will be forced away from the magnet and will propel the lock element 68 along with it and this will rethereby prop lf, the lock element 68 forwardly and e act on th v lever 66 to start it to'rock clockwise whereupon t will fall clockwise by gravity and releasing Lposition as described,I by the hook 69,

and in order to. prevent the hook from becoming disengaged by vibration or the like and to give it a more hook-like-` character, the hook 69 may be provided with ariinclined face 'I2 andthe arll mature may have a corresponding inclined face 13 engageable by the inclined face 12.

In the present brake construction, as in other brakes in which the brake shoes are pivoted outwardly of the brake shoe lining, in order that they may float and always conform to the contour of the drum, the shoes are apt to rotate on their pivots by gravity and cause the upper part of the brake lining to ride on the drum and wear it more than the rest of the lining, which of course, reduces the effective braking area of the lining; and this is overcome in the-present brake by the following construction, comprising the devices illustrated in Fig. l directly under the lowermost portions of the brake shoes.

These devices are preferably alike and a descriptionof one of them will therefore suffice. Reference may also be had to Figs, 7, 8, 9, and 10.

A bearing block 14, is mounted on the main frame, preferably upon the transverse brace member 2 by bolts or the like 15.and a. pivot pin 18 is mounted thereon extending laterally therefrom and on the pin is mounted for oscillatory movement a disc 11having a notch 18 in its periphery extending at an angle to the radius of the disc and the bearing of the disc on the pin is preferably below its center. A spring 19 surrounding the pin reacts upon the disc and upon an enlarged pin head 88 and holds the disc in frictional engagement with the block; and to equalize wear effected upon oscillatory -movement of the disc,

the frictional engagement.v of the disc and blockV is caused to occur on an annular surface 8| provided on the block.

A finger construction 82 on the lower end of the brake shoe carries a pin 83 lying transversely in the slot 18.

In the operation of this device, when the brake Y shoe is retracted to release the brake, the brake shoe pivot pin, for example the pin 38, moves radially away from the drum. If theshoe should tend to `rotate by gravity around the pin 38, as referred to, the pin 83 prevents it by its engagement with the side of the slot 18. This action is shown diagrammatically in Figs. '1 and 8 in going from Fig, '1 to Fig. 8. In these two figures and in Fig. 1, the slot 18 is shown in the position, which it would assume when the brake is new and the brake shoe linings are thick.

If the disc 11 were rigidly mounted. on the frame, then as the brake shoe linings wear, the engagement of the pin 83 with the edges of the slot 18 would interfere with the free floating of the brake shoe and it is for this reason that the disc is made frictionally movable. Because of this frictional yielding support for the disc, each time that the brake shoe is moved to its braking position, the pin 83 by engagement with the other side of the slot 18 gradually Vrotates the disc around its frlctional pivot and after the brake linings have worn a great deal, the disc and the disc slot will be in positions indicated diagram matically in Figs. 9 and 10 where in going from Fig. 9 to Fig. 10 the above described act-ions will be seen to occur, The device thus not only prevents the gravitational fall or drooping of the brake shoes when in their released condition, but automatically compensates and/adjusts itself for wear of the brake shoes so that it operates with equal effectiveness for all thicknesses of brake shoe linings.

It is not essential that the disc 11 be circular as shown; in fact it is not essential that it be in any sense a disc. A disc has been shown because this is the most convenient form or shape to 'manufacture and because it is the most convenient way to provide surfaces 84 and 85 at the sides ofthe slot 18 for the following purpose. When assembling the brake shoe on its own pivot pin, the pin 83 should first be placed in the slot 18, otherwise, for the optimum shape and direction of the slot 18, it might be. impossible to positionthe pin 83 in its slot. By providing the said surfaces 84 and 85, the engagement of the pin with these surfaces will make it impossible to insert the brake shoe pivot pin. These surfaces therefore compel the assembler to first put the pin 83 in its slot 18 before inserting the brake shoe pivot pin s o that both pins are sure to be properly assembled with their coordinate parts. It is believed therefore that it will now be apparent that the surfaces 84 and 85 are not essential; but that when they are provided they compel a proper assembly of the parts the first time; thereby avoiding trial and error; and that when these surfaces are provided they may be provided by anysuitable configuration off the material in which the slot 18 is provided. s

In the foregoing description, the various pins, such for example as the pins 34, 38, 48, I4, 49, 4E, and 41 are described as having implied means to hold them from moving longitudinally out of the structure; and as is well known it is preferred to mount them loosely in their bores so that they can upon occasion be removed. It is preferred in the presentstructure that such pins be removable but the means for rendering them removable has been omitted from the principal figures of the drawing in the interest of simplicity and the preferred means is shown separately in Figs. 14 to 16 inclusive.

The pins project longitudinally beyond the parts which they connect and are provided with circular grooves 88 in the pin near their ends; and a spring wire bent generally in the form of a hair pin is formed to grip the pin in the groove so that the spring wire, which may be referred to as a cotter, prevents endwise shifting of the pin, although the grooves are so located as to allow some clearance between the cotter and the part adjacent to it. It is understood that such hair pin cotters are old but an improvement has been made here which overcomes one of the objections to such cotters. In practice it has been found that when the cotters are removed they are laid aside and by the time that they are wanted again for replacement, they become lost or damaged; and the improvement here disclosed, while permitting movement of the cotter to disengage it from its pin, which it is intended to retain, is prevented from removal from the apparatus. This is accomplished by providing the cotter with sides 81-81 which converge toward each other and by mounting the closed end of the hair pin cotter on a headed pin 88 driven' or threaded into the apparatus at a convenient point near to the main pin. When the cotter is withdrawn from the groove of the main pin to release the latter, the converging sides 81 of the cotter grip the supplemental pin 88 thus resiliently mounting the cotter on the apparatus near its point of use.

In brakes of this general class, it isdesirable to be able to remove the drum out of the brake in the direction radial to the drum with the least possible disturbance or disassembly of the brake parts and this advantage is provided for in the present brake as follows.

Referring for example to Fig. 1, the U-shaped member 59 may as was described be rotated around into the broken line position 59A. One

all.

o! the pins 40 or 49 preferably the pin 40mey then be removed as described andthe tie bar rocked out of the way around the remaining one o! these pins. After this simple operation. the drum 'I may be raised vertically out of the brake structure during which the brake shoeswill rock on their own pivots out of the way of theidrum.-

In Figs. 17 and 18 is illustrated a modification of the support for the stop 58. Here this stop, designated as 58A, completely encircles the tie rod instead of being in the nature of a slotted stop embracing only the upper half of the tie rod. The functions f this stop are the same as those of the stop 58 described hereinbefore. In this case, however, to remove the stop support `Gand the tie rod to permit removal of the drum, both pins 40 and 49 would be removed; and then the U-shaped moment produced thereby is so small as to be negligible.

As to the stresses on the framel occasioned by the torque of the rotary drum transmitted to the f frame by the shoes gripping the drum, these the .drum rotates in one direction or the other,Y

tangential force is transmitted through the frame 4I to the pin or shaft 41 and thence to the member 59 with its stop y58 and the tie rod itself would all be revolved out of the way around the pivot pin I4, as shown in going from Fig. 1'7 to Fig. 18. v f

In brakes of this general class, stresses are set up during operation of the mechanism to set the brake; and stresses are set up by the torque developed in the mechanism by the rotatory drum while being brought to rest and being vheld at rest by the brake shoes.`

,These stresses are transmitted to the frame which supports the mechanism; and to -resist them and thereby hold the' parts in their intended relative positions for correct functioning,

the frame must ti rigid. In prior brakes, where l this necessary rigidity is provided it is usually built into the frame itself by making the frame suiilciently strong, without regard to the directions in which the stresses are developed; and in consequence the frames have been unduly bulky, heavy, and expensive.

It is one of the advantages vof the present brakey that the aforesaid stresses act upon the frame with very little or no bending moment, fwhereby a light weight, simple frame is rendered sufllciently strong to counteract them.

As to ther stresses on' the frame occasioned by operation of the mechanism, these strains result from the forces holding the brake shoes against the drum. As to the left hand brakeshoe, as viewed in the drawing, this force is developed in the frame 4| acting as a lever, pivoting on the shoe pivot 46, and is transmitted to the base shaft 41, and its direction is longitudinal of these base members and there is no bending moment at As to the righthand shoe, this force is developed in the frame as a lever, rocking on the shoe pivotV 38, and is applied to the lever atits lowerend at the pin 34 by the magnet spring;

and the line of action of the force is horizontal vertically to the base members I-i, so that the frame in vertical directions, and the horizontal distance from this pin to the adjacent transverse base member is so small (and in fact could vreadily b'e made zero) that bending moment on the main frame is negligible. l

Considering the right hand shoe, in either direction of rotation of the drum. Vertical tangential force is transmitted to the frame 30 through the shoe pin 38. and thence vertically to the pin 34, and thence vertically through the armature to the pin I4, and thence through the short rigid arms l3.-I3 to the vmagnet frame, and thence bending moment in the main frame is represented by the moment arm distance from the middle of the magnet supporting bracket I0 to the adjacent',- transverse base member 2; and this distance can be made smaller and smaller by positioning the said base member 2 nearer and nearer to a point directlyunder the magnet. The location of this base member 2 as shown in the draw- .members I-I oi' the main frame at the pin or ing has been found to reduce the bending moment in the main frame to a negligible quantity.A

At the left hand end of Fig. 1, I have shown the base members l-l as continuing into feet 9| at right angles to the direction of the members I-l; and this has been done to illustrate that the brake mechanism can be mounted either horizontally (as viewed in Fig. 1) or vertically as it would be if it were supported by these feet 9| on a horizontal support.

n The brake mechanism of this invention will operate equally well in the horizontal or vertical position as referred to; and when in the vertical position, the spring 80 may in some cases not be needed, gravity, in such cases performing its y function.

that part thereof to the left of the section line 3-,3 in Fig. 1.

and substantially parallel with the main frame g base members I-I. This force reacts horizontally on the pin 34 and on the magnet frame at its point of attachment to the base members I-I and is therefore so near to the base members that the bending moment of the force with respect to the base members is so small as to be negligible. In the development of this brake, the parts were originally so arranged that this line of force reaction was located between the base members I-I so that the bending moment on the base members was zero: but it was found to be more convenient to arrange the parts with this line of force reaction slightly above them and it has been placed there in the final design, because the My invention is not limited to the exact details of construction, proportions and relation of parts, illustrated vand described. Changes and modifications may be made, and my invention comprehends all such modifications and changes which come within the scope of the appended claims.

Iclaim:

1. In a locking mechanism for an electromagnet, comprising a. magnet and an energizing windf ing therefor and a spring-movable magneticallyretractable armature; an armature latch having a magnetic armature-engageable latch portion and biased to move from an armature engaging to an armature disengaging position; a pivoted lever connected to the latch and movable in two directions', to correspondingly propel and retract the latch; va lever latch engageable with the lever to hold it in one direction and biased to tend to move to lever disengaging position; the armature latch when in armature engaging position being retractable by the lever upon movement thereof in said one direction to retract the armature through a portion only of its stroke; and the lever latch being operable to `hold the lever in that position; the amature being retractable through the rest of its stroke upon energization of the winding and magnetically adhering to and retracting the armature latch; and the lever being thereby movable to eifect disengagement of the lever latch by its bias; the amature upon being spring-moved upon subsequent de-energization of the winding, propelling the latch and causing movement of the unlatched lever in the direction to further propel the amature latch out of armature engagement.

2. In an electromagnetic brake comprising spring-set brake shoes retractable by the armature of an electro-magnet upon energization` thereof; operator-operable means to lock'the armature in retracted position comprising: an

armature-engageable latch; a lever to move the y latch to retract the armature; a lever latch to hold the lever with the armature retracted through only a part of its total stroke, and biased to tend to move to lever unlatching position; and the armature latch comprising a magnetic portion which adheres to the armature upon energization of the electro-magnet and effects movement of the armature latch and lever and unlatching of the lever, upon energization of the electromagnet and the consequent movement of the armature through the remainder of its stroke.

3. In a magnetic brake construction, a, main base disposable under a brake drum; a rst mechanism frame member pivoted at a lower portion to' the base, extending upwardly therefrom, pivotally supporting a nrst brake shoe at an intermediate portion, and supporting a rst tie rod bearing at 'an upper portion; an electromagnet comprising a magnet frame supported at a lower portion thereof on the base, and at an upper portion supporting an amature bearing; a swinging armature depending from the amature bearing; a second mechanism frame member pivotally connected atl a lower portion to a lower portion of the armature, and pivotally supporting a second brake shoe at an intermediate portion, and at an upper portion supporting a second tie rod bearing; the brake shoes being disposed at opposite sides of the drum, and the tie rod bearings being spaced apart; a tie rod construction connecting the tie rod bearings and comprising means to adjust its length; abutment means carried by the tie rod and movable adjustably along the tie rod; and stop means engageable by the abutment means.

4. The construction described in claim 3 and in which the said first mechanism frame member is biased in the vdirection to disengage its assoelated shoe from the drum and to effect engagement of the abutment with the stop means.

5. The construction described in claim 3 and in which the swinging armature is disposed between the electromagnet and the said second mechanism frame member: and the said second tie member bearing, the said second shoe bearing, and the said pivot connection to the armature are all three in substantially a common plane.

6. The construction described in claim 3 and in which the said stop is disposed above the drum and is hingingly movable away from the abutment and disposable out of the path of the drum construction.

7. The construction described in claim 3 and in which the tie rod lies above the drum and is detachably supported in the tie rod bearings whereby it may be removed out of the path of the drum when the latter is moved upwardly out of the construction.

8. The construction described in claim 3 and in which the base is provided with mounting means disposed to support the construction with the base at a side of the drum.

9. In a magnetic brake construction, a main base; a rst mechanism frame member pivoted at a lower portion to the base, extending upwardly therefrom, pivotally supporting a rst brake shoe at an intermediate portion, and supporting a first n tie rod bearing at an upper portion; an electromagnet comprising va magnet frame supported on the base, an armature bearing supported adjacent to an upper Vportion of the magnet frame; a swinging magnet armature depending from the armature bearing; a second mechanism frame member pivotally connected at a lower portion to a lower portion of the armature, and pivotally supporting a second brake shoe at an intermediate portion, and at an upper portion supporting a second tie rod bearing; the brake shoes being disposed in confronting spaced relation, and the tie rod bearings being spaced apart; a tie rod construction connecting the tie rod bearings and comprising means to adjust its length; abutment means on and movable with the tie rod and movable adjustably along the tie rod; and stop means engageable by the abutment means.

10. In a magnetic brake construction, for cooperation with a rotary brake drum, a main base; a rst mechanism frame member pivoted at a lower portion to the base, extending upwardly therefrom, pivotally supporting a first brake shoe at an intermediate portion, and supporting a first tie rod bearing at an upper portion; an electromagnet comprising a magnet frame supported on the base, an armature bearing supported adjacent to an upper portion of the magnet frame; a swinging magnet armature depending from the armature bearing and electromagnetically attractable toward the magnet frame, and a spring to retract it; a second mechanism frame member pivotally connected at a lower portion to a lower portion of the armature, and pivotally supporting asecond brake shoe at an intermediate portion, and at an upper portion supporting a second tie rod bearing; the brake shoes being disposable at opposite sides of the drum, and being provided with renewable linings for engaging the drum, and the tie rod bearings being spaced apart; a tie rod construction connecting the tie rod bearings andcomprising means to adjust its length; abutment means on and movable with the tie rod and movable adjustably along the tie rod; and stop means engageable by the abutment means, when the brake shoes are retracted from the drum upon energization of the electromagnet, and movable away from the abutment when the brake shoes are moved by the spring to engage the drum upon de-energization oi. the electromagnet; the extent of movement of the stop means away from the abutment being inversely commensurable with the worn thickness of the brake shoe linings.

11. In a brake of the type comprising brake shoes disposable on opposite sides of a brake drum and movable toward the drum to engage it to set the brake and movable away from the drum to 17 clear it to release the brake; a frame; supports for the shoes: means interconnecting the shoe the v lever moving idly without engaging 4the arsupports: mutually engageable stop elements',v one on. the interconnecting means and one supported by the frame; engaged when the brake is re leased andspaced apart when the brake'isset; the spaced distance vci the separated; atop lele`- ments being proportional to the clearanoebtween is released and .increasing yas'gthel "brake shoesv wear; the said stop 'elements- Being disposed so` that .the sai-d spaced distance is readily observable and indicates at all times the shoe-and-drumclearanceand the state of wear ofthe shoes;

` and means to adjust the length .of the internen-,

nesting means eil'ective to adi/ust the shoe-and-y drum clearance to take up fori'wear.

v12,'In a brake o1' thetypefcomprlsing' brake shoes disposable on opposite drum and .movable toward theldrum to engage j it to set the brake and movableaway from the 32 drum to clear itl to release t'hebrake; aframezv mature; anad a latch for holding the lever and lock element in armature retracted position.

14. In combination with the spring-movable magnetically-retractable magnetic armature of an electromagnet, and a frame lsupporting the magnet and armature: a movable lock element: a

pivotally supported lever, movable in alternate disupports for the shoes: a tie ,rod i'1 iterconnecting1"" and increasing as the brake shoes wear; ths'said so f stop elements' being disposed so that their positions relative to each other are readily observable andl indicate at all-,times the:"f'shoc-and-fdruxnll clearance and the state of wear ofthe shoes: and

take upi'or wear. j

magnetically-retractable vsnfmatu're of an electro-'f o magnet. 'and a frame supporting the vmagnet-and r armature: alock element''supported forfmovement manuallyin one direction to'an operative f position and biased :or mov'exnentin, the opposite direction. to anidle position.- andreciprocable in both positions;l v a lever movable to reciprocate the means to adjust thelensth of the tie rod j `tive to. adjust the shoe-and-drum clearance to' L 1 l Numberlock element; the ll'ock'element inthe .operative position beingjout ot'rengagement with the' armature, and being reciprocable @by-'fthe lever inone direction to'enga'ge the armature-zandretract itagainst the force of the spring; and the lock ,ele-1 lllllt whsnreciprocatsd `the idlepositionbyl e .1 3ate 1,154,791 Sept. 28; 1915 i-,358,339 Novi 9,1920 H1,696,906 Jabxow oct. 2.1928 2,059,244 Kiekhaefer Nov.. 3. 1936 750,288 Hoover etal. Jan. 2 6, 1904 1,967,479 pfleger Juiyi24, .1934 2,087,478 Hodgson July 20, 1937 9,987,895 Bierenreid 1u1y a7. 1937 1,199,871 Burton e -.-goct.,s, 191s 1,295,3871 ":Peycle ...v fFeb. 25,1919 2,130,595 .Mueller ...f.-;'.' Bepft. 20. 1938 v 1,672,314 Hall June 5. 1928 1,852,857 Price Apr. 5, 1932 2,314,451

rections to move the look element forwardly and to. retract it: the lockelement being movable 'manually to a position ln which, when retracted vby movement of the lever, a portion of the lock element moves into engagement with the armature and retracts it against the force of the spring through a portion of the armatures retractable movement; and the lock element being biased to a normal position in which when retracted by the f lever the said portion thereof moves 'without engaglng the armature; a movableflatchli'or hold-v .v s ing the lever and lock element in said armature?.` ,i -retracted position and biased toward a released -position; the said portion of the lock element .being magnetic and being caused to adhere to' :the `armature magnetically -tocause the lock element 'to move `with the amature when the latter isfmoved. through the rest of its magnetically-y retractable movement by the magnet; andthe lock element thereupon moving they lever to eiTect l release otfthe'lever holdinglatch.' y

, s i m www E91 The followinrreierencesfare of '111.90111 in he ville of this patent: l l

UNITED s'ra'rastra'rm'rs 

